An overwhelming problem faced by public telephone service providers is theft of transmitters and receivers located in the telephone handset. To combat this problem, service providers have established mechanical disassembly requirements to which public phone manufacturer should conform. These requirements impose that telephone handset caps should not be removable from the telephone handset without destroying the handset. (Generic Requirements for Public Telephone Handsets, TR-TSY-000452, Issue 1, Bellcore, 10/87). In order to determine whether a public telephone handset conforms to such a requirement, manufacturers have stressed the telephone handset to failure, which many times have rendered the tested handset unusable regardless of whether it passed or failed the requirements test. Such catastrophic testing has resulted in a higher cost to be borne by the manufacturer and passed on to the public phone service provider. Furthermore, smaller sample sizes were tested in the interest of reducing costs associated with such destructive testing which directly resulted in reduced quality control.
To alleviate the problems and high costs associated with catastrophic testing, service providers are changing their mind set on requirements needed to counter vandalism and theft problems. Requirements are changing to reflect the need for the handset to withstand a maximum torque which a strong human hand could apply to the handset cap in an attempt to remove it. This revised requirement has great potential to significantly reduce costs and improve quality control associated with testing public phone caps; however, suitable equipment to facilitate testing and an associated test method do not exist for determining conformance with evolving requirements.
The lack of such test equipment and method hinders the evolution and implementation of requirements which support non-destructive testing. Under current requirements, test methods typically include the use of a pipe or belt wrench which are not suitable to perform torque tests on handset caps under evolving requirements.
In placing a pipe wrench onto the cap of a public phone handset and applying a torque by attempting to turn the wrench, a number of drawbacks exist that preclude the use of this tool under evolving test requirements. The shape and grip of the pipe wrench does not conform to the shape of the handset cap; therefore, the pipe wrench applies pressure at only two points where the wrench actually makes contact with the cap. As a result, the torque applied is non-uniform and test results are non-reproducible. Furthermore, even applying a torque using the pipe wrench at levels short of destruction is undesirable since deformation and elongation of the cap and handset will result due to the two-point, non-uniform pressure being applied by the pipe wrench.
Although a belt wrench appears to conform geometrically to the cylindrical shape of the handset cap, the tool still proves ineffective since the belt wrench is cylindrical with non-sloping sides and the handset cap has sloping sides; therefore only a small linear area of the belt wrench actually contacts the handset cap, thus resulting in a non-uniform torque being applied to the handset cap. Due to insufficient contact with the handset cap, both the pipe and belt wrenches tend to slip off the cap when torque is being applied, thus presenting a hazard to the user. Furthermore, to date torque measurement instruments are not adaptable to these wrenches such that the torque being applied to the handset cap can be quantified or measured. Even if adaptable measurement instruments existed, pipe and belt wrenches would prove ineffective since the measurements would be non-reproducible given the poor contact between the wrench and the cap and the non-uniform torque applied to the handset cap.
In view of these shortcomings of conventional handset cap test instruments, it is the object of the present invention to provide a device and method which facilitate the uniform application of torque to handset cap and the nondestructively and reproducibly quantification of torque applied to the cap to determine whether the cap can withstand a pre-determined torque without separating from the telephone instrument.